fuse

Bussmann ®
Introduction to
Low Voltage
Fuse Technology
Bussmann is one of the world's leading manufacturers
of circuit protection solutions, producing and marketing
over 30,000 product variants for use within most
industries - Electrical Distribution, Electronics,
Telecommunications, Automotive, Space and Military.
Established in 1914 Bussmann now employs over 2,500
personnel world - wide, working together to provide the
high level of service and product quality for which the
company is renowned. Over one billion Fuses are
produced per year in production facilities in the U.K.
Denmark, Mexico, Brazil and the USA.
Striving for continual improvement, Bussmann focus
on value added activities, reducing wasted resource and
encouraging involvement at all levels. All our products
are approved by the leading regulatory authorities and
reflect a high level of quality.
Through our people, processes and products we at
Bussmann aim to provide Total Customer Satisfaction.
Bussmann ®
Circuit Protection Solutions
Bussmann
®
INTRODUCTION
Selecting, specifying or recommending a Fuse Link for a particular application
can be critical and carries with it a great deal of responsibility. It is reassuring to
know that the Fuse Link selected is the result of over 100 years of experience and
cumulative knowledge gained in the invention, design, development and
manufacture of Fuse Links.
Information recorded in a letter from a W H Preece to the Society of Telegraph
Engineers in 1887, stated that Fuses had been used to protect cables since 1864.
The earliest enclosed Fuse Links were patented by Edison in 1880, but these
were air-filled. The primary purpose of the glass envelope in which the Fuse
Link elements were enclosed was to prevent molten droplets falling from the
element, and to relieve the tensile strain on the element. In 1890, W M Mordy,
chief engineer of the Brush Electrical Engineering Company, patented the first
cartridge Fuse Link filled with arc-quenching materials. This device comprised a
copper foil or wire conductor enclosed in a glass tube filled with a granular
material. The filler could be chalk, sand, marble or any number of substances.
Development in Fuse Technology has come a long way since the early days of
Edison and Mordy. More recent developments have been incremental, with
evolutionary improvements in design offering better performance. However
the phenomena that occurs during the fusing of the elements is still shrouded in
some mystery. When a Fuse conductor (or element) melts and interrupts the
current, a very powerful "ARC" bridges the gap. This "ARC" is nearly as hot as
the surface of the sun and although small in size it contains a tremendous
amount of energy. Computer modelling of Fuse Link behaviour is now helping
designers to better understand these mysterious processes that occur when a
Fuse Link operates.
The majority of Fuse Links are designed and tested for compliance with one or
other of the recognised standards, and whereas a section of these notes will
cover "Standards and Approvals" frequent reference will be made to the terms;
Fuse Link and Fuse, and therefore we should define the difference. A Fuse Link is
a device with a strip or element of easily melted metal placed in an electric circuit
so as to interrupt an excessive current by melting. The term Fuse is referred to
when a Fuse Link is fitted into a Fuse Holder, or when mounted onto a Fuse
Block, therefore the Fuse comprises all the parts that form the complete device.
Fuse Links are an important component used in almost every electrical
installation, protecting both equipment and personal safety. Bussmann Fuse
Links are manufactured under Quality Systems independently assessed to
BS5750 Part 2 ( ISO 9002 ) and many ratings carry the ASTA 20 endorsement.
You can be assured that at Bussmann we offer the customer the highest level of
Bussmann
quality and integrity across every product line.
®
one
THE WEAKEST LINK
All electrical equipment that we use; lighting, domestic The sand filler packed
appliances, motors, heaters etc., together with the cables around the element helps
connecting them, are designed to operate safely provided that to carry away the heat
only the normal current flows. Occasionally things can go generated due to the
wrong: the cable insulation wears away, motors suffer overloads, resistance of the
and people drop a spanner in the works, or across live terminals. elements. The ceramic
The immediate effect of any such incident is for the current to rise body forms the outer
to a value far above what is safe for the rest of the system to carry. housing, while the metal
The consequence is usually overheating which can lead to fire or caps and fixing tags lead
even explosion. This is when the Fuse Link comes to the rescue - the current into and out
it is the specially designed weak link in the chain. When the of the Fuse Link.
current in the system rises above a prescribed danger level the
conductors ( thin wires or strips of metal; the element ) inside the Fuse Link Operation:
Fuse Link melt and form a gap so that the current is safely
interrupted and the rest of the system is saved from the
consequence of the fault. a) When normal load
current flows, the
elements get quite hot
Fuse Links are complex devices to design, not only must they but the heat is
react quickly in the event of a fault and interrupt the current carried away by the sand
without damage to the system, they are also expected to have a a n d t h e m e t a l
long service life when carrying normal current. Few things are connections so the
more annoying to a user than a Fuse Link operating needlessly elements don't reach their
when there is no actual fault. Spurious operating is inherent in melting temperature.
alternative protective devices dependent on mechanical
operation such as miniature circuit breakers.
b) If the current flow
rises above the rated
The heart of the Fuse Link is the wires or strips of metal which current of the Fuse Link,
carry the current. These must be designed to melt and break the the elements get much
current flow when the current rises above a certain value. These hotter and the excess heat
wires or strips of metal are called the elements. cannot be carried away
quickly enough. The
Thin elements carry less current than fat ones, therefore a Fuse element therefore
Link rated to carry 1 Amp of current will obviously have far reaches melting
thinner elements than a 100 Amp Fuse Link. For larger current temperature and breaks.
ratings we do not have to use a very fat element, instead we use The current is then
several thinner ones running alongside each other or in parallel. interrupted and the Fuse
In practice a 1 Amp Fuse Link might have a single thin wire Link has done its job.
element, while a 1000 Amp Fuse Link, one of the largest ones we
manufacture, could have many thick strip elements. For this
reason, Fuse Links of high current rating have much larger bodies
than small ratings.
two
INSIDE A FUSE WHEN IT IS OPERATIVE
A - Arc burning away ends of element.
B - Hot Ionised gas carries current
between broken element ends.
C - Sand grains are molten to form
glass ‘tube’.
D - Sand grains stick together to form
pumice stone - like mass called
‘Fulgurite’.
E - Element wire or strip.
F - Fuse Body
G - Sand Filler
three
FUSE LINK CONSTRUCTION
A Fuse Link is a safety valve, its presence in an electrical circuit Connectors and Outer
must permit full flow of energy to the equipment or installation Caps: These are of copper
which it serves without contributing in any way to potential or brass, the connectors
weakness during normal function. However, the link must still (tags) being fixed to the
maintain the ability to react when a fault condition occurs within end caps by welding and
the circuit, containing the fault energy within the body of the soldering or by riveting
Fuse Link. Construction and characteristics are therefore the key and soldering. The whole
features in the Fuse Link design and operation. Let us now component is electro-
consider how the fault energy is contained within the Fuse Link tinned. Current rating or
by examining the construction of a typical Fuse Link. reference numbers are
stamped on either the cap
The Fuse Link Body: This is produced to very precise dimensions or the tag.
from high grade ceramic or fibre material which must be able to
withstand the high thermal and mechanical stresses which occur The Bussmann range of
when the Fuse Link operates. Industrial Fuse Links is
manufactured in eleven
The Element: The very heart of the Fuse Link. Operating body sizes covering
characteristics are the key feature of every Fuse Link, as they ratings from 2 to 1250
control the action of the Fuse Link under operating conditions, Amps. A number of tag
and consequently its prospective capability in an over-current forms exist including
situation. Specific parameters are usually based on the current those preferred by BS88.
surge over a measured period of time (referred to as I t) as on The Bussmann range of
graphs. To achieve such exacting characteristics the choice of Industrial Fuse Links
element material is a very important factor. Silver plated copper meet the requirements of
or silver elements manufactured to close limits are constructed. BS88 Parts 1, 2 and 6 and
On each strip element there are accurately machined restrictions, IEC269 Parts 1 and 2 in
the configuration of these being designed with the aid of a voltages of 240, 415, 550
computer to provide the required operating characteristics. and 660.
Conditions of small overloads are controlled by the use of special
alloy melted onto the elements. These are known as the ‘M’
effect.
Filler: A quartz filler of controlled size, free from organic and
metallic impurities and in a moisture free form, is compacted into
the ceramic body.
Inner Caps: These are made of copper or brass and electro-tinned.
They are interference fitted to the ends of the ceramic body and
the outer caps are then pressed on to them ensuring a good
mechanical fit and sound electrical connection.
Discs: These are used to provide resilience between the inner
and outer caps and act as an arc barrier.
four
Connector and Outer Cap
Disc
Inner Cap
Body
Fuse Elements
Inner Cap
Disc
Connector and Outer Cap
Filler
five
FUSE LINK CHARACTERISTICS
Fuse Links are used in a variety of applications, each having its the Fuse Link under
own special requirements. It is necessary to design Fuse Links onerous conditions of
specially for different applications. It is, of course, possible to maximum arc energy.
meet many different applications with the same basic design, Two values or curves are
however certain circuits, such as motor starting, protection of always given for each Fuse
semiconductor devices, dc operation, etc., may require specially Link:
designed Fuse Links. Fuse Link operation must be considered 1)minimum pre-melting
under three different conditions; normal running conditions, I t and
small sustained overload conditions, heavy overload or short 2)maximum clearing I t.
circuit conditions. Therefore when designing and selecting a Fuse
Link for a particular application, the operating characteristics are The first represents the
the most important consideration. amount of energy let
through by the Fuse Link
Time-Current Characteristic: A characteristic of all Fuse Links is from the start of the fault
that the speed at which they operate is directly linked to the level up until the time the Fuse
of the fault current. Example: a 100 Amp Fuse Link might take 10 Link actually begins to
minutes to operate at 200 Amps but would operate in one tenth of operate. The second
a second at 1000 Amps. A graph plotting the operating time of a represents the total
Fuse Link against fault current is called a Time - Current graph. package of energy let
Time - Current curves are produced according to BS or IEC through by the Fuse Link
Standards, which are termed average curves. This average allows until the instant when the
for manufacturing tolerances on a given type of Fuse Link. Time - Fuse Link finally
Current curves according to North American Standards are interrupts the fault
plotted differently with each Fuse Link design having two curves. current.
These represent the fastest time that the Fuse Link would operate
for given values of current. The second plots the slowest time that
the same Fuse Link would operate at the same currents.
Cut-Off Characteristics: When a Fuse Link interrupts a high
value of fault current, it chops off the current before it has time to
reach its full value, in other words the Fuse Link current - limits.
Current limiting is the most important feature of Fuse Link
operation as it ensures that cables, motors, transformers and other
equipment are protected from the potentially catastrophic effects
of many thousands of amps of fault current which could
otherwise flow. The rate at which the Fuse Link chops off the
potential fault current is shown on the cut-off current graph.
It or Joule-Integrated Data: A calculation of energy which is
controlled or cuts off through the Fuse Link, by convention this
energy is sometimes referred to as the Joule-integral. The
calculation of this current let through is more commonly referred
to as the I t formula (current let through by the Fuse Link, squared
multiplied by the time in seconds for which the current flows)
These values represent the total operating and pre-arcing times of
six
Examples
1. Time-current characteristics 2. Cut-off Current Characteristics
Fuse cut-off current
Time
Current Current
3 (a) I t Characteristics 3 (b) I t ‘Bull Rushes’
Amp Seconds
Amp Seconds
Current Current
seven
DEFINITIONS
HRC or HBC: High Rupturing Capacity or High Breaking Capacity
denotes the ability of the Fuse Link to interrupt extremely high fault currents.
Rated Voltage: The maximum voltage that the Fuse Link is designed to
interrupt. Rated voltage may be in volts ac, dc or both. Fuse Links are voltage-
sensitive devices, and it is important to note that satisfactory operation of a
Fuse Link under fault conditions is dependent upon the applied voltage. They
must not therefore be applied in circuits above their voltage capability. They
can however be used satisfactorily in circuits at lower voltages.
Current Rating: The value of current that a Fuse Link will carry
continuously without deterioration under specified conditions. The
continuous current rating of the Fuse Link should not be less than the full load
current of the circuit.
Minimum Fusing Current: The minimum value of current to cause
melting of the fusible elements.
Rated Breaking Capacity: The highest value of fault current that the Fuse
Link has been tested to interrupt e.g. 80 kA. The standard values of breaking
capacity are 80kA for voltages of 415V ac. and above, 40kA for dc.
applications. The 240V ac. designs have a breaking capacity of 50kA.
Power Dissipation: The power released in a Fuse Link carrying rated
current under specified conditions. The quoted power dissipation of a Fuse
Link must be the maximum value at the extremity of the tags. The power
loss values relate to a maximum test ambient temperature of 25 degrees C.
Discrimination: In determining if discrimination occurs between two Fuse
Links in a circuit with a fault, the minor Fuse Link should operate and leave the
major Fuse Link unimpaired.
Time/Current Characteristics: To comply with the requirements of BS88
(or other relevant standard) the time/current characteristics must lie within
specified zones. These zones have the minimum pre-arcing time and
maximum total operating time at 415 volts as their limiting values. All the
Bussmann standard current ratings fall within the limiting values of the time /
current zones.
Ambient Temperature: Fuse Links are thermal devices and as such may
require some de-rating when used at elevated ambient temperatures. A de-
rating in terms of current of 0.5% per degree centigrade above an ambient
of 35 degrees C is recommended.
eight
Fuse: A device which by the fusing of one or more of its components opens
the circuit it is inserted in by breaking the current when this current exceeds a
given value for sufficient time. A Fuse comprises all the parts that form the
complete device.
Fuse Holder: The combination of the Fuse-Base with its Fuse-Carrier.
Fuse Carrier: The moveable part of a Fuse, designed to carry the Fuse Link.
Fuse Base: The fixed part of a Fuse including terminals, contacts and covers.
Switching: Ability to make and break defined load and overload currents at
a rated operational voltage, for the useful life of the device.
Switch: A mechanical device capable of making, carrying and breaking
current under circuit conditions.
Switch Fuse: A switch connected in series with the Fuse, or Fuses to make a
composite device.
Fuse Switch: A Fuse, or a number of Fuses, mounted on the moving contact
system of a specially designed switch.
Short Circuit: Short time current capability and/or through fault and/or
fault making capability.
Protection: Overload and short circuit interruption.
Isolation: Ensures disconnection of the supply for safe working.
Full Range Fuse Link: A Fuse Link with a full range breaking capability,
capable of interrupting all currents from rated breaking current generally
down to the minimum fusing current.
Current Limiting Fuse Link: A Fuse Link which during its operation
limits the circuit current to a value much lower than the peak value of the
prospective current. In practice, the terms HRC and current limiting are
synonymous.
Back-up Fuse Link: A Fuse Link with partial range breaking capability
having a minimum breaking current greater than the minimum fusing
current.
nine
LOW VOLTAGE FUSE LINKS TO BS88 & IEC269
The Bussmann range of high breaking capacity Fuse Links for Low Voltage industrial
and General Purpose applications meet the requirements of BS88 and IEC269. By using
advanced Fuse technology the current ratings up to 400 Amps have compact
dimensions but are still within the standardised dimensional and performance
requirements. These designs have been optimised for 415 / 240 Volt systems. The
standard range of Fuse Links are available from 2 to 1250 Amp in the following tag
forms: Offset Blade - Offset Bolted - Centre Bolted.
Supplementary ranges cover applications up to 660 Volt ac and 500 Volt dc including
those with non-standard tag fixings.
The Bussmann range of Fuse Links for the protection of Semiconductor Devices were
introduced in 1965. Manufacturer's literature will refer to these Fuse Links as high
speed, fast acting, or for semiconductor protection. Unfortunately there is no
universally recognised term, however in British practice the dimensions of these Fuse
Links are quite different to those for normal Industrial use so there is no possibility of
fitting the wrong type. Bussmann offer two voltage ranges, 240V ac / 150V dc (6 to
900Amps ) and 660V ac / 450V dc (6 to 700Amps ) .
The Bussmann range of Low Voltage Feeder Pillar Fuse Links are designed for use with
wedge type fuse carriers with fixing centres of 82mm and 92mm. These are primarily
for use by Electricity Supply Industries in distribution pillars, open type substations
boards, heavy duty service cut-outs and underground disconnecting boxes.
Standards:
BS88: Part 1 ( IEC269 - 1 ) General Requirements.
BS88: Section 2.1 & 2.2 (IEC269-2) Additional Requirements for Industrial
Fuse Links (bolted tag).
BS88: Part 3 - 1 ( IEC269 - 3 ) Additional Requirements for Household
Fuse Links (domestic).
BS88: Part 4 ( IEC269 - 4 ) Additional Requirements for
Semiconductor Protection Fuse Links.
BS88: Part 5 Additional Requirements for Electricity
Supply Network (Feeder Pillar) Fuse Links.
BS88: Part 6 Additional Requirements for Compact Fuse
Links (bladed tag).
UTILISATION CATEGORIES
gG Full Range breaking capability, General Application
gM Full Range breaking capability, Motor Application
aM Partial Range breaking capability, Motor Application
aR / gR Semiconductor Protection, Fast Acting ( Superflink )
gTr Transformer Protection
FUSE STANDARDS:
Most electrical equipment is sold as complying with some relevant standard or
specification. The familiar Kitemark and British Standard number is familiar on most
domestic appliances and is the only guarantee of quality that the user has. The majority
of our Fuse Devices are designed and tested for compliance with one or more of the
recognised fuse standards.
IEC Standard (International Electrotechnical Commission) is now accepted by
most countries world-wide, and many countries such as UK, Germany, France,
Australia, India etc. have altered their own National Standards to comply with IEC.
Therefore, if we confirm to the user that our Fuse equipment complies with the relevant
IEC Standard, this will usually be acceptable.
VDE Standard ( Verband Deutscher Elektrotechniker ) In Germany, VDE 0660 for
Low Voltage Fuses has been aligned with the relevant IEC Standard. The dimensions of
German Fuse Links (now widely adopted in many parts of the world) are specified to Din
43620 for Low Voltage Fuse Links. Note: Din (Deutsche Industrie Norm) is a
dimensional standard only.
UL Standard (Underwriters Laboratories) In the USA, standards are quite different
from those adopted in Europe. Electrical tests are specified in standards written by UL.
Low Voltage Fuse Links have dimensions according to NEMA (National Electrical
Manufacturers Association)
CSA Standard ( Canadian Standards Authority ) In Canada, Low Voltage Fuses
have to comply with CSA, which is a mixture of UK and USA practice.
The harmonisation of standards developed from the International Electrical
Certificate ( IEC ) is being adopted for use in Europe with European Norm ( EN )
under a slightly different name, for example Fuse Links tested to BS/IEC269 will in
future be approved to BSEN60269.
eleven
FROM SUB-STATION TO TABLE LAMP
Electricity sub-stations which we can see in our neighbourhood securely fenced, receive power via
cables at 11.000 volts. This supply is transformed down to 415 volts, using what is known as a
distribution frame. The supply is broken up into several separate 240 volt outlets which run via
cables under the adjacent streets to our homes. Each outlet on the distribution frame is protected by
a Fuse Link known as a Feeder Pillar or J-type. This Fuse Link protects the entire length of
underground cable from the sub-station to our domestic meter.
Protecting the supply at the front end of our domestic meter, is the House Service Fuse Link (Types
KR85 or LR85). These Fuse Links are designed to ensure minimum temperature rise within their
sealed box ( commonly referred to as cut-outs ) but at the same time to chop the fault current down
to a low enough value to save any miniature circuit
breaker in the consumer unit (miniature circuit breakers
Feeder Pillar
(typical) cannot stand high fault currents as well as Fuse Links).
315MJ30 Reassuring to know that our domestic consumer units
incorporating miniature circuit breakers are backed up by
the tried and tested Fuse.
From the House Service Fuse Link, current flows via the
meter to a consumer unit where the supply is split up as
required (lighting, ring mains, cooker etc). Protecting each
Transformer
11,000 V supply
of these circuits could
be a Consumer Unit
Fuse Link, although it is
common practice to
install miniature
circuit breakers into
the domestic consumer
unit. Consumer Unit
Fuse Links are rated at
240 volt and are
available in current
Plug top PTC13
ratings 5 to 45 Amps.
C15 C45
The Plug Top Fuse
Consumer Unit
Link is the final link in
this protective chain,
which began with the
KR85
(typical)
Feeder Pillar Fuse.
House Service Plug Top Fuse Links
are rated at 240 volt
with current ratings 1
to 13 Amps.
twelve
LOW VOLTAGE FUSE APPLICATIONS
From Power Station to the Home, Fuses play a vital part in protecting electrical circuits. Bussmann
manufacture a wide range of Fuse Links, from the large hand made version used in power distribution
systems to the tiny, surface-mount chips on the circuit boards inside electronic equipment. Fuses are
probably the most common of all electrical components used in electrical circuits. The following chart
gives just a few of the many applications utilising the Low Voltage Fuse.
1. Main Incomer.
2. Main Fuse Combination
Switch (distribution
Power Station 10 board).
Commercial
9 Site 3. LV Motor Rated (AC
Motor).
Industrial Site 4, 5 Distribution Fuse Board.
6, 14, 15 Feeder Pillar.
Housing 7. Switch Fuse.
7 11 Estate 8. LV (Office Equipment).
5
9. LV Fuse in Holder (Air
8 18 Conditioning plant).
12 17 10. LV Motor Rated (Air
13 16 Conditioning plant).
1 11. Power Semiconductor
2 3 4 6 (standby power supply).
12. LV Fuse in Holder
(lighting).
14 15 13. Street Lighting.
16. House Service.
17. Consumer Unit.
18. Plug Top (electric fire).
Diagram courtesy of Electrical Review.
MOTOR CIRCUIT PROTECTION
In motor circuits the Fuse Link has to withstand the starting current of the motor, typically 7 x full load
current (FLC) for the run-up period in the case of direct on line (DOL) start motor, and provide back up
protection with the motor starter and associated cables. Extended dual ratings of motor protection
Fuse Links with gM characteristics are available in most popular sizes of Fuse Links.
thirteen
FUSE LINKS FOR THE PROTECTION OF SEMICONDUCTORS
The term semiconductor in electrical circuits can best be described as a switch, however
unlike the domestic light switch, there are no moving parts. When a small amount of
electricity is applied to one part of the semiconductor, the complete device changes from
being an insulator (a material that does not pass electric current) to a conductor (a material
that does pass electric current). Like many other circuit components, the semiconductor is
sensitive to excesses in both current and voltage. When an over-current is evident the wafer
thin sections of the device over-heat and are damaged. Similarly, when the current is not
flowing through the device, but a high circuit voltage is present, the construction of the
device will again be damaged.
Semiconductors were first marketed in 1953, and it was realised from the outset that these
devices had very limited overload capacities and, as they were expensive, the Fuse
manufacturers attempted to produce Fuse Links which were more sensitive to overloads
and which would operate more quickly than their conventional designs. Fuse Links
designed to protect semiconductors incorporate elements machined to finer tolerances and
rarely employ the M-effect as used in the Industrial range. A Fuse Link element with finer
tolerances will reduce the ability of the Fuse to provide low over-current protection, and
will therefore provide increased protection to the semiconductor. As a consequence of
interrupting the current flow more quickly, an over-voltage is produced by the Fuse Link.
This voltage must be limited or other circuit components (including the semiconductor)
could be damaged. To limit this over-voltage, additional bonding agents are added to
improve the sand compaction around the element, reducing the energy of the arc on
operation. The Fuse Link body material may also be of a higher grade material, and the end
connections may employ a solid metal construction or be assembled using higher
temperature solders.
Element for Industrial Applications
M Effect Alloy
Element for Semiconductor Applications
fourteen
Manufacturers and users alike, will refer to these Fuse Links as Protection of expensive
'high speed', 'fast acting', or, 'for semiconductor protection'. semiconductors can only
Unfortunately there is no universally recognised term, though be achieved by devices
in British practice the dimensions of the Fuse Link are quite having an extremely
different to those for the normal Industrial use, so there is no rapid circuit breaking
possibility of fitting the wrong type. action coupled with
cur rent and energy
limitation. The Fuse
In the UK, the majority of power semiconductors are used in Link is the only device
three-phase and single-phase circuits operating at 240V per
available at an economic
phase. Fuse Links are dimensionally standardised to comply
price, which is fast
with BS 88: Part 4, and are available for single-phase
enough in operation to
applications with ratings up to 900Amp at 240Volts. They are
protect semiconductors.
also available for use in three-phase circuits operating at 660V
Fuse Link operation
in current ratings up to 710 Amps. The standard dimensions
depends upon the heat
are as small as practicable because many Fuse Links are used in
generated by the passage
applications where space is at a premium.
of excess currents in
specially designed
The square-ceramic NH' dimensioned designs are very popular, elements. This gives the
the body lengths being much shorter than those used for Fuse Link the important
Industrial applications. End terminations suitable for bolted property of current
connection with fixing centres at 80 or 110mm are widely used, limitation in clearing
but alternative versions with tapped holes in the ends are fault currents, i.e., the
available. The latter design has the advantage of being more Fuse Link element melts
compact and it is normally used for ratings above 1000 Amps. before the first peak of
The overall dimensions of Fuse Links for semiconductor the fault current is
protection are specified in DIN 43653. reached. This therefore,
limits the magnitude
Many Fuse Links for the protection of semiconductors used in and duration of the fault
Europe incorporate indicators. These are similar to those used current. Fuse Links do
in Industrial Fuse Links and they may be either positioned at not depend upon any
one of the ends or in the central regions of the Fuse Link body. As mechanical system,
well as giving local indication as to the status of the Fuse Link, with inherent inertia, in
these devices may be adopted to operate microswitches so that their mode of operation
remote indication of the Fuse operation may be provided. and therefore Fuse Links
are able to respond
Fuse Links provided in North American circuits containing immediately to the
semiconductors are similar in construction to those used in thermal state of
Industrial applications. However, as in the UK, the special semiconductors.
performance requirements have been obtained by using
suitable materials and element construction. The dimensions
of these Fuse Links have not been standardised by any national
body but industry standards have evolved by usage in the
voltage ratings of 130, 250, 500, and 700.
Range of Semiconductor Devices
fifteen
NH' FUSE SYSTEM
The NH' Fuse Link designs ( blade type ) are used in factory distribution systems and in the
distribution cabinets of the electricity- supply industry protecting power-distribution
networks. NH' Fuse Links are generally available for applications up to and including 1600
Amps, for ac. cicuits operating at levels up to 500v, and dc. circuits of voltages up to 440v.
Designs with restricted current ratings are available for 660v ac. systems. NH' Fuse Links
incorporate indicators, a feature which is not normally provided on low voltage Fuse Links to
British Standard.
NH - NIEDERSPANNUNGS HOCHLEITUNGS
( Low Voltage High Breaking Capacity )
Din - DEUTSCHE INDUSTRIE NORM
( German Industry Norm )
VDE - VERBAND DEUTSCHER ELEKTROTECHNIKER
(German Electrotechnical Association)
Construction of Part No:
AMP + NH + BODY SIZE + CHARACTERISTIC
Example: 100 + NH + C00 + G ( gL ) = 100NHC00G
100 + NH + 00 + M (aM) = 100NH00M
100 + NH + 00 + G (gL-660V) = 100NH00-660
Body Sizes: Maximum Current Rating (Amps)
C00 100 Amps
00 160 Amps
0 160 Amps
1 250 Amps
2 400 Amps
3 630 Amps
4a / 4 1600 Amps
Voltages:
400v ac.
500v ac.
660 / 690v ac.
800v ac.
Note: System Voltage must be less than rated voltage of theFuse Link.
sixteen
seventeen
D' /'DO' TYPE FUSES (End - Contact or Screw - Type)
This is an old type of Fuse System, often referred to as Bottle type, clearly stemming from the
characteristic shape of the Fuse Link. There are two designs, the 'D' (Diazed) and the 'DO' (Neozed).
D' Type Fuse Links are manufactured to Din Specification 49365 and 49360 and have delayed, quick
acting or ultra quick acting characteristics. They conform to VDE regulations 0635 for line Fuse
Fittings with totally enclosed Fuse Links rated 500 volts. The ratings available range from 2 - 100 amps.
These Fuse Links are fitted with operation indicators which
generally take the form of a button head which is pushed out
through the end contact by a weak spring when the Fuse Link
operates.
'DO' Type Fuse Links with advanced compact design
features of a cooler running Fuse Link, giving advantages in
space saving, performance and reliability are considered to be
the successor to the 'D' type. 'DO' Fuse Links are suitable for 440
volt ac with 10% excess capability. Tested to IEC 269 - 1
specification and this design is approved by Lloyds Register of
Shipping. Ratings range from 2 - 63 amps.
A standard range of ceramic Fuse Bases is available to
accommodate the range of both 'D' and 'DO' Fuse Links. Gauge
rings are supplied to ensure that the correct Fuse Link is installed
to protect the selected circuit. The gauge rings are colour coded
for ease of identification.
eighteen
CYLINDRICAL FUSE LINKS
Fuse Links with cylindrical bodies and ferrule end caps are now widely used for both
domestic and industrial applications. Ratings up to 45 Amps for use in 240 volt ac are
available for domestic circuits. We are all familiar with the tried and tested designs of the Plug
Top and Consumer Unit Fuse Links which have been protecting our domestic appliances for
many years. For industrial applications, Fuse Links with ratings up to 125 amps are produced
for use in circuits in which the voltages do not exceed 500V. The Cylindrical types, available
for protecting industrial circuits, are becoming more popular, replacing the 'D' and 'DO' types
in new and refurbished installations. We can also claim that Cylindrical designs are now
beginning to replace the BS 88 small dimensioned designs with bladed tags up to 63 amps.
The more popular sizes of Cylindrical Fuse Links for industrial applications are:
8.5 x 31.5mm, in ratings 0.5 - 25 amps. (500V ac up to 20 amp/400V ac at 25 amp)
10.3 x 38mm, in ratings 1 - 32 amps. (500V ac up to 25 amp/400V ac at 32 amp)
14 x 51mm, in ratings 2 - 50 amps. (500V ac up to 32 amp/400V ac at 40 & 50 amp)
22 x 58mm, in ratings 6 - 125 amps. (500V ac up to 100 amp/400V ac at 125 amp)
Cylindrical Fuse Links are approved to IEC 269, and are available in gL and aM categories.
The 10 x 38, 14 x 51, and 22 x 58mm Fuse Links have a breaking capacity of 100 kA.
The 8 x 31.5mm has a breaking capacity of 50 kA.
nineteen
NORTH AMERICAN FUSE LINKS
The internal demand for electrical equipment is so great in the Fuse Links to North
USA that Fuse Links unique to the home market have been American designs are not
developed. Several types of Low Voltage Fuse Links are available dissimilar in appearance
with current ratings up to 6000 amps, with the ability to operate to BS/IEC designs in that
at voltages of 250V or 600V. ratings up to 60 amps are
generally Cylindrical,
In order to develop safety test procedures, agencies regulating and higher ratings are
the test procedures have developed basic performance and fitted with blade type
physical specifications or standards for a product. These tags for mounting in
standards have culminated in the establishment of distinct spring contacts, and
classes of Low Voltage Fuse Links, the main classes being: either bolted or slotted
tags which allow for
Class R - up to 600 amps, 250V and 600V bolted connection.
Class H - up to 600 amps, 250V and 600V Ceramic bodies are used,
(The Class R Fuse Link has a high breaking capacity of 200 however the Class R Fuse
kA, whereas the Class H has a low breaking capacity of 10 Link bodies are usually
kA) made of materials
ranging from vulcanised
Class J - up to 600 amps, 600 V fibre, to pultruded
Class L - from 600 amps to 6000 amps, 600 V thermoset polyester.
The elements are
generally made of copper
but silver is used when
the let-through energies
under high faults are to
be kept to a low level.
The dual element Fuse
Link employs a centre
section which does not
require any sand filling
material. This is because
the metal parts slow the
temperature rise and
allow free movement of
these metal parts when
clearing an overload.
twenty
Class CC Fuse Links
600V, 200,000 ampere interrupting rating, branch circuit fuse links with overall dimensions of
!
/! x 1½ inches. Their design incorporates a rejection feature that allows them to be inserted into
rejection fuse holders and fuse blocks that reject all lower voltage, lower interrupting rating
!
/! x 1½ inch fuse links. They are available from 0.01 amps to 30 amps.
Class G Fuse Links
480V, 100,000 ampere interrupting rating branch circuit fuse links that are size rejecting to
eliminate over fusing. The Fuse Links’ Diameter is !/! inch while the length varies from #/ $ to 2¼
inches. These are available in ampere ratings of 1 amp to 600 amps.
Class H Fuse Links
250V and 600V; 10,000 ampere interrupting rating branch circuit fuses that may be renewable or
non-renewable. These are available in ampere ratings from 1 amp to 600 amps.
Class J Fuse Links
These fuse links are rated to interrupt a minimum 200,000 amperes AC. They are labeled as
‘Current Limiting’, are rated for 600 Volts AC and are not interchangeable with other Class K fuse
Links. These are fuse links listed as k-1, K-5 or K-9. Each subclass has designated I t and I F
maximums. These are dimensionally the same as Class H fuse links and they can have
interrupting ratings of 50,000; 100,000 or 200,000 amps. These fuse links are current limiting.
However, they are not marked ‘current limiting’ on their label since they do not have a rejection
feature.
Class K Fuse Links
These are fuse links listed as K-1, K-5 or K-9. Each subclass has designated I t and I
maximums.
F
These are dimensionally the same as Class H fuse links and they can have interrupting ratings of
50,000; 100,000 and 200,000 amps. These fuse links are current limiting. However they are not
marked ‘current limiting’ on their label since they do not have a rejection feature.
Class L Fuse Links
These fuse links are rated for 601 to 6000 amperes and are rated to interrupt a minimum of
200,000 amperes AC. They are labeled ‘current limiting’ and are rated at 600 Volts AC. They are
intended to be bolted into their mountings and are not normally used in clips. Some Class L fuse
links have designed-in time delay features for all purpose use.
Class R Fuse Links
These are high performance fuse links rated at
/ to 600 amps in 250 volt and 600 volt ratings.
All are marked ‘current limiting’ on their label and all have a minimum of 200,000 Amp
interrupting rating. They have identical outline dimensions with the Class H fuse links, but have
a rejection feature which prevents the user from mounting a fuse of lesser capabilities (lower
interrupting capacity) when used with special Class R Clips. Class R fuse links will fit into either
rejection or non-rejection clips.
Class T Fuse Links
A industrial class of fuse links in 300 and 600 volt, with ratings from 1 Amp to 1200 Amps. They
are physically very small and can be applied where space is at a premium. They are fast acting and
time-lag fuse links, with an interrupting rating of 200,000 Amps RMS.
twenty-one
MINIATURE FUSE LINKS
Although miniature, domestic plug-top and other small dimensioned Fuse Links are physically
similar, they are grouped into several different application categories and must comply with
different specification standards. Many different types are available with current ratings from
32mA to 20A, most have cylindrical type bodies and ferrule-type end caps, though an increasing
number are produced for ease of fitting on to printed circuit boards (PCBs) Miniature Fuse Links are
covered by the IEC standard (IEC127)
Parts; 1, 2, 3, 4.
IEC 127, Part 1, Covers the definitions and general requirements
IEC 127, Part 2, Covers Cartridge type Fuse Links
IEC 127, Part 3, Covers Sub-Miniature type Fuse Links
IEC 127, Part 4, Covers Universal Modular Fuse Links
The category of speed of operation are also signified by internationally accepted letters that are
marked on the Fuse Link. The letters and corresponding categories are as follows:
F Quick-acting
FF Super-quick-acting
M Medium-time-lag
T Time-lag or Anti-surge
TT Super-time-lag
DOMESTIC PLUG FUSES
The UK plug and socket system is so familiar that we take it for granted. Fused plugs and
sockets have provided a level of safety in the home since 1947. The Fuse Links used are
commonly referred to as 'plug-top cartridge' (PTC) and are available in a range of current
ratings up to 13A. Cylindrical in design, 25.4mm in length, with a diameter of 6.35mm and
complying with the requirements of BS 1362. The two preferred ratings of 3A and 13A also
conform with IEC 269. The Bussmann range of PTC Fuse Links, catalogue reference TDC180
are available in ratings of 1, 2, 3, 5, 7, 10, and 13Amp, at 240V ac. They are ASTA Certified and
have the BSI Kite Mark Licence..
twenty-two
TYPE 2 CO-ORDINATION
Motor starter manufacturers undertake evaluation and certification tests for the protection of their
motor starters with Fuse Links and recommend the maximum Fuse Link that can be used for
protection. These recommendations usually do not state any specific Fuse Link manufacturers type
number and they often refer to gG Fuse Links in accordance with IEC269 or the equivalent national
standard e.g. BS88: Part 2, VDE 0636/21 or UL requirements. This gives a simple and effective means
of co-ordination, since a Fuse Link selected in accordance with manufacturers recommendations to
withstand inrush currents will normally give adequate short circuit protection to the motor starter.
A working group of the IEC Low Voltage Fuse Committee has been studying the co-ordination of
Fuse Links with modern motor starters and have concluded that Fuse Links with pre-arcing I²t
characteristics towards the lower end of the gG characteristics of modern IEC269 Fuse Links, protect
modern IEC contactors. This includes an evaluation of test information supplied by Fuse and motor
starter manufacturers. The equivalent category of duty to the old 'Class C' in the new IEC standard
947-4-1 is 'Type 2'. In addition, a recent IEC Working Group Applications Guide concludes that
modern gG Fuse Links to BS88-2, BS88-6 and IEC269-2 will generally be quite suitable for the
protection of compact IEC motor starters.
Bussmann offers a wide range of Fuse Solutions for the protection of motor circuits and as a leading
manufacturer is appreciative of the need to endorse Type 2 Co-ordination requirements when
advising on Fuse applications.
twenty-three
FUSE HOLDERS: BRITISH STANDARD TYPES
There are two distinct designs of British Standard Fuse Holder; BS88: Part 2, with popular ratings
of 20, 32, 63, and 100 amp. These Fuse Holders accommodate offset bolted tag Fuse Links to BS88:
Parts 1 & 2, 1988 (IEC 269- 1 & 2 1986). A 200 and 400 amp version is available, however at ratings
above 100 amps, a more cost effective solution is to install a Fuse Switch Disconnect. BS88: Part 6,
with popular ratings of 32, and 63 amps, accommodate offset blade tag Fuse Links to BS 88: Part 6,
1988. A 125 amp is available (GEC only).
The present day Fuse Holder has many features, one being that live metal cannot be touched when
the Fuse Carrier is being removed from or inserted into the Fuse Base. The cable terminals within
the Fuse Base must also be fitted with barriers or shutters so that live metal is not exposed when
the Fuse Carrier is removed. The Bussmann Camaster range, which accommodates offset bolted
tag Fuse Links, is fitted with a Cam for ease of removal from the Fuse Base allowing significantly
improved contact pressure between the Fuse Carrier contacts and Base contacts, with an enhanced
electrical performance level. This design overcomes the major problem of all other manufactures of
British Standard Fuse Holders world-wide who have to compromise between difficulties of Fuse
Carrier removal from the Base and achievable contact pressure. The standard front connected
Camaster Fuse Holder can be readily converted from front connected to front/back stud
connected, and double back stud connected with the use of a unique back stud accessory and a
screw driver.
The patented Safeloc Fuse Holders provide a simple safe range
designed to accommodate the compact range of offset blade tag
Fuse Links. Safeloc offers significant savings in volume and cost
as well as a reduction in fitting time, and power loss. These Fuse
Holders incorporate a unique slide/snap action Carrier which
eliminates the need for Fuse Carrier contacts. This provides
positive, stress free fitting of the Fuse Link and locks the Fuse
Link in position ensuring safe insertion and withdrawal from
the Base. Safeloc Fuse Holders provide a safe and easy method of
protecting a wide range of electrical equipment such as lighting,
heating, motor and control circuits.
twenty-four
FUSE HOLDERS: MODULAR TYPES
This design of Fuse Holder is a definite spin-off from the miniature
circuit breaker (mcb) frame design. The need for a comparable Fuse
package, similar in overall dimensions to the MCB was needed, but
with improved performance. Modular Fuse Holders accommodate
Cylindrical type Fuse Links, and therefore global acceptability can
be achieved using the one 10 x 38mm design incorporating Fuse Link
ratings 0.05 - 32 amps. The 10 x 38mm designs are manufactured to
European IEC, North American UL, and Canadian CSA Standards.
Modular Fuse Holders are the most
versatile of all Fuse Holders available,
offering Fuse protection in three
popular sizes up to a maximum Fuse
Link rating of 125 amps:
Size 10 x 38mm Accommodating
Fuse Links 0.05 - 32 amps
Size 14 x 51mm Accommodating
Fuse Links 2-50 amps
Size 22 x 58mm Accommodating
Fuse Links 16 - 125 amps
Features of the Bussmann 10 x 38mm Modular Fuse Holder:
Dovetail design provides maximum flexibility in the
assembly of multi - poles.
Touchsafe design IP20 - No exposed metal parts.
Din rail mounted ( 35mm )
Optional open Fuse indication lights.
Available in single pole or multi-pole configurations.
Bussmann Modular Fuse Holders are excellent for switchboards,
control panels, protection of small motors, transformer protection,
and many more industrial applications.
twenty-five
LOW VOLTAGE SWITCH AND FUSEGEAR
A definitive description is difficult as both Switch and Fusegear
products are perceived as being part of the same family of equipment.
One distinction that can be made is that finished Switchgear cubicles
tend to be custom designed and therefore can require heavy investment
in both financial and human resource. Fusegear is usually described as a
range of stand alone enclosed Fuse components which can be installed
as individual units or stacked into a modular distribution system.
Switch / Fusegear covers quite a variety of devices, all intended to carry
out the function of controlling and protecting electrical circuits so that
the electricity supply can be safely utilised.
The following symbols have been agreed internationally and are based
on IEC 617 - 7.
Diagram courtesy of E.I.E.M.A.
Whilst at first sight these definitions appear complex and confusing,
each device has its own specific features and functions, and there is logic
to the terminology. The use of one or more of these terms in the
description of a device defines and identifies the function of the device.
In addition the position of the word 'Fuse' at the beginning of the
description identifies that the Fuse forms part of the moving contact
system. The word 'Fuse' at the end indicates a static Fuse. It is important
to note that the definitions do not indicate whether the device is
capable of being isolated at both ends of the Fuse. Where this is not the
case adequate marking of the line / load terminals is essential for safe
use.
Following the introduction of the 16th Edition of the IEE (Institute of
Electrical Engineers) Regulations for Electrical Installations, which is
now BS 7671: 1995, the subject of isolation has been prominent and the
Industry Standard now calls up the requirement of BS 60947 - 3 for all
disconnects (isolators).
twenty-six
SWITCH FUSE OR FUSE SWITCH?
Quite simply, a Switch Fuse is a combination of Isolator Switch Given that you don't
(usually rotary type) and Fuse or Fuses connected in series to want unauthorised
make a composite device. A Fuse Switch, on the other hand, is persons tampering with
when the Fuse or Fuses are mounted on the moving contact the supply, either turning
system of a specially designed switch. The position of the word it on or off, or actually
'Fuse' in the description is important; at the beginning of the gaining access to live
description it identifies that the fuse forms part of the moving circuits, look for
contact system. The word 'Fuse' at the end indicates a static fuse. enclosures that offer
Without confusing the issue, what then is a Switch Isolator? features like lockable
Basically view the Switch Isolator as a simple switch that is used handles locking in the ON
to isolate a circuit after the load has been turned off. It is not to be or OFF position.
used to isolate a circuit under load.
Switch Fuses and Fuse
The Bussmann Compact range of Switch Fuse tends to be a Switches are still the
stand alone unit housed in an enclosure, usually sheet steel. And most reliable and easy to
is a tried and tested approach to distribution networks, install approach, offering
switching, isolating and for protecting individual loads. A Fuse the busy engineer a high
Switch is commonly found being used on urban secondary level of quality and
distribution networks up to 22Kv. A Fuse Switch is generally appropriate test
regarded as safer because the circuit cannot be in the live state approvals.
when a fuse is being replaced and, unlike a Switch Fuse it cannot
be closed on a fault between the switch and the fuse. Although
selection and specification really depend upon the application,
either device should have the ability to carry rated current either
continuously or for a period of eight hours under defined
conditions. Often the question is raised in respect of the neutral.
Where the neutral is reliably earthed it is accepted that the
neutral need not be switched except in defined circumstances ie.
Incoming switch in the consumer unit, even though the Wiring
Regulations (BS7671) class the neutral as a live conductor. For
applications where the neutral should be switched
simultaneously with the phase(s) or alternatively may be
arranged to make before and break after the phase(s).
The descriptive terminology used for many years has now been
changed. The European norm (BSEN 60947) now refers to the
simple switch as a switch disconnector. Basically under IEC 617-
7 the terms 'switch' 'disconnector' and 'fuse' are used together
in such a way as to describe the actual function of the device. A
good reference to the new terminology can be found in
diagrammatic format on the previous page, everything from the
accepted symbol for the simple switch right up to the more
complex fuse switch disconnector.
twenty-seven
COMPACT SWITCHFUSES AND SWITCH ISOLATORS
Bussmann offers a versatile range of reliable and easy to install
surface/wall mounting Compact Switchfuse and Switch Isolator
units for distribution and motor circuit protection applications.
Designed and tested in accordance with the requirements of
BS.5419:1977 and IEC947- 3:1990. The Switches are ASTA certified
up to 50 kA at 415V ac with the appropriate BS88 Fuse Link.
Switchfuses:
20, 32, 63, and 100 amp units at 415 volts ac Single Pole & Neutral,
Triple Pole & Neutral.
Switchfuse complies with the definitions in IEC947- 3 for 'Switch
Disconnector - Fuse'
Switch Isolators:
20, 32, 63, and 125 amp units at 415 volts ac Triple Pole, Triple Pole &
Neutral.
Switch Isolator complies with the definitions in IEC947- 3 for 'Switch
Disconnector‘
Additional ratings available in British designs are: 200, 315, 400, and
630 amp. These Switch Disconnects can be specified as enclosed or
un-enclosed units.
FUSE COMBINATION SWITCHES
The Bussmann range of Fuse Combination Switches is designed and
tested in accordance with BS EN 60947- 3, 1992 complying with the
definitions for 'Fuse Switch Disconnector'
A range of enclosed triple pole and neutral, and un-enclosed triple
pole units are available with ratings from 63 to 630 amps.
Within Europe, harmonisation of the electrical industry is being
achieved by CENELEC (Comite Européen de Normalisation
Electrotechnique) which produces, whenever possible, European
Standards based on the work of the IEC. Adoption of the European
Standard within the EEC is mandatory. In the UK such standards are
further endorsed with the additional BS prefix, for example BS EN - - -
twenty-eight
HRC DISTRIBUTION FUSE BOARDS
Camaster Distribution Fuseboards feature 3 phase Fuse Banks, Neutral Bar and Earth Bar
available in 32 amps, 63 amps, 4 to 12 outgoing ways and 100 amps, 4 to 8 outgoing ways.
Fully insulated and shrouded busbars and Fuse Holder base terminals provide complete
personnel protection against direct contact of live parts. The range is complemented with
the innovative 32 amp Distribution Fuseboard packaged into the traditional 20 amp
dimensions offering the end user economies in size and cost. Camaster Distribution
Fuseboards accommodate bolted tag Fuse Links to BS88:Part 1 and 2, 1988. The Fuseboards
fully comply with the requirements of BS5486:Part11, 1989 and can be ordered as factory
built assemblies in single pole and neutral or triple pole and neutral. The degree of enclosure
protection is IP42, however an IP55 level of protection is also available.
Safeloc Distribution Fuseboards are available in 32 amp and 63
amp outgoing ways utilising the Safeloc Fuse Banks which
accommodate offset blade tag Fuse Links to BS 88: Part 6; 1988.
The Fuseboards fully comply with the requirements of BS5486:
Part 11: 1989 with a protection standard of IP42 to BS EN 60947-1.
They are also available to higher specification of IP55. Single pole
and neutral or triple pole and neutral Fuseboards can be ordered as
factory built assemblies. The fully insulated busbars and shielded
Fuse Holder bases contacts provide complete internal personnel
protection against direct contact electric shock.
Camloc is a unique Distribution Fuseboard System, comprising a family of innovative
components. The main Pan Assembly is fitted with either an integral on-load isolator or
direct connection facility. The system has a fully shrouded, centrally mounted busbar
arrangement fully rated at 200 amps. This is designed for plug in Fuse Holders which take the
offset blade tag Fuse Links to BS88:Part 6, 1988. A range of accessories complete the package.
The Fuse Holders rated at 16, 32, and 63 amp are of uniform size. Mixed rating capability can
therefore be achieved. The Fuse Holders have special Z stab connectors so that they can be
plugged in directly onto the central busbar. The Camloc Distribution Fuseboard System has
all the flexibility of the miniature circuit Distribution Board but with an increased breaking
capacity of 50 kA.
twenty-nine
N H ( H R C - LV ) F U S E S W I T C H
DISCONNECTOR (for fuse links sizes: C00,
00, 1, 2 and 3)
The NH Fuse Switch Disconnector (part
reference LBS) is completely insulated and
touch protected. It consists of thermically
stable self extinguishing synthetic material.
There are no metal parts except the current
carrying contact system. The contact system
is torsion resistant, the metal parts of the fuse
switch disconnector are corrosion resistant,
the copper contacts are either silver or nickel
galvanised with stainless steel springs. The
requirements exceed those demanded in
applicable standards (IEC, VDE, OVE etc).
The protection cover, produced as one-piece
or two-piece, depending on size, is snapped
into the switch base.
Upper as well as lower touch protection
cover can be sealed and protected against
unauthorised opening. (Size 00 to size 2).
The switch door and the hinges consist of
impact resistant synthetic material. In the
ON position a flexible lock arrests the
retractable switch door. In the OFF position
the switch door can be removed to change the
fuse links. Large windows placed in the
switch door allow a view of the label and
indicator of the fuse links. The windows are
equipped with pierceable testing holes to
check the switching condition of the fuse
links.
The NH Fuse Switch Disconnector is
approved to the following standards:
IEC408; VDE0660; ÖVE; SN40; IEC947;
SEV1089; KEMA3104-90 - 3106-90.
thirty
NH VERTICAL FUSE SWITCH DISCONNECTOR.
A Low Voltage Vertical Load Break Fuse Switch
Disconnector to take NH style fuse links in size 00
Acc. DIN43620/1 and IEC269-2-1.
Assembly.
Switch Base: is isolated and touch protected (degree
of protection IP2Lx).
Base Body: consists of glass-fibre, which is
strengthened thermically, has high-stability with
self-extinguishing properties. There are no metal
parts except the current carrying contact system.
Contact System: the one-piece contact system with
stainless steel springs, is corrosion resistant as well as
torsion resistant. The copper contacts are nickel
galvanised or, on special order, silver coated.
Protection Cover: the one-piece protection cover
consists of a glass fibre strengthened, thermically
high stable and self extinguishing thermoplastic,
free of halogen. It is snapped into the base body and
does not have to be removed for mounting.
Switch Door: in ON position a flexible lock arrests
the attachable door of the vertical fuse switch.
In OFF position the door can be removed to change
the fuse links.
Label and indicator of the fuse links can be seen
through large windows placed in the switch door.
The shiftable windows are equiped with testing
holes to check switching condition of the fuse links
or voltage. After withdrawing the test leads the front
degree of protection IP3Lx is again re-established.
The switch door can be sealed in closed position; the
switch door can be parked (parking position). These
approved to IEC947-3.
thirty-one
Notes
ASSURANCE:
Since the initial conception of the idea, the HRC Fuse Link has undergone considerable evolution
and sophistication. The device, originally designed simply to isolate circuits and to protect
equipment and personnel against the dangers of high overloads, today finds an application in
almost every electrical installation, from television to space research, from plug-top to nuclear
power station. This is a continuous process and there is no doubt that in the years to come there
will be further improvements in the design and manufacture of Fuse and Fusegear equipment, so
keeping in step with the ever-changing requirements for circuit protection.
ACKNOWLEDGEMENTS
The application of Fuses is detailed in the book "Electric Fuses" written by A Wright and P G
Newbery. Copies can be obtained from The Institute of Electrical Engineers or alternatively from
Bussmann. Wright and Newbery's classic guide to the world of electric Fuses has now been
substantially revised and remains the comprehensive reference work on the subject. We also
acknowledge the work of Mr D.Whitaker for writing and compiling this training manual.
Additional publications: Guide to Fuse Link Application and Guide to Switch & Fusegear Devices,
both available from EIEMA (Electrical Installation Equipment Manufacturers Association) or
alternatively Bussmann.
The information contained in this publication is intended to introduce the reader to the basics of Fuse Technology and should not be
used to assist in the design, construction or maintenance of any electrical installation. Bussmanns' policy is one of continuing
improvement, we reserve the right to supply Fuse Data/Catalogue information and Product which may differ from that described
and illustrated in this publication.
thirty-two
Bussmann
®
ADDING VALUE THROUGH TECHNICAL SUPPORT
As part of our commitment to Customer satisfaction, Bussmann provides extensive,
knowledgeable technical support for all major product lines. Our team includes
experienced engineers in Europe, North America and Asia - engineers who can provide
expert advice about the best way to protect specific circuits and applications.
Contact our Applications Engineers on: Telephone +44 (0)1509 882760 or 766
Facsimile +44 (0)1509 882768
Bussmann produce and distributes a wide range of product catalogues, data sheets
and technical bulletins - many of which can be obtained through an automated fax
response system. (Bussmann Information Fax: 001 314 527 1450)
Contact Marketing Communications on: Telephone +44 (0)1509 882715
Facsimile +44 (0)1509 882794
Contact Customer Services on: Telephone +44 (0)1509 882600
Facsimile +44 (0)1509 882786
Bussmann has manufacturing operations in the UK, Denmark, and the USA which
have earned ISO 9000 certification. Bussmann customers are assured of only the
highest possible level of service and quality across every product line.
Worldwide Web http://www.bussmann.com
Bussmann
®
Most of today's industrial markets recognise no
international boundaries, they are driven by global
companies and influenced by international standards
and product designs.
Bussmann is committed to a programme of product
development, ensuring that we remain the first fuse
company to offer and support a truly world-wide
product line.
Bussmann provides extensive technical support and
can offer expert advice on the best way to protect
specific circuits and applications. Technical support
capabilities also include high power testing in the Paul P.
Gubany Centre, which is the only test centre capable of
generating 300.000 ampere fault current. The Gubany
Centre makes it possible for Bussmann and Customers
to evaluate the reliability and performance of new
products under the most extreme fault conditions.
Our goal is to provide circuit protection solutions
anywhere in the world, for a broad range of
applications.
®
Circuit Protection Solutions
http://www.bussmann.com
Bussmann Division, Cooper (UK) Limited, Burton-on-the-Wolds, Leicestershire LE12 5TH UK Tel: 44 (0)1509 882600 Fax: 44 (0)1509 882786
A Industries Company !" # % "#